A phase varying apparatus for use with an engine is structured to controllably vary the opening/closing timing of an intake-side or exhaust-side open-close valve of the engine in accordance with an operational state. For example, a valve timing control apparatus has been proposed as this kind of phase varying apparatus. This valve timing control apparatus is made up of a rotational member to which a rotational force is transmitted from a crankshaft, a camshaft formed integrally with a cam by which an engine valve is opened and closed, a phase adjusting mechanism that is disposed between the rotational member and the camshaft and that adjusts a relative rotational phase of the camshaft relative to the rotational member by receiving an electromagnetic force, an internally hollow cylindrical member that is disposed on the side of the rotational member or on the side of the camshaft and that is extended in the axial direction, an electromagnetic generation portion that is rotatably borne by the cylindrical member and that applies an electromagnetic force onto the phase adjusting mechanism, and a backlash absorbing mechanism that absorbs the backlash or play of the electromagnetic generation portion (see Patent Literature 1). In this valve timing control apparatus, the electromagnetic generation portion is borne by the cylindrical member, and a space is formed inside the cylindrical member, and hence the entire apparatus can be lightened. Additionally, the electromagnetic generation portion is supported by a cover through the backlash absorbing mechanism including an elastic body, and hence, even if a force in the axial direction is applied to the electromagnetic generation portion from the camshaft side so that the electromagnetic generation portion is displaced in the axial direction, the backlash or play of the electromagnetic generation portion caused by this displacement can be absorbed by the backlash absorbing mechanism.
Patent Literature 1: Japanese Published Unexamined Patent Application No. 2005-299604 (see pages 4 to 8, FIG. 1.)